Trailers pulled by vehicles such as cars, trucks, sports utility or similar vehicles are extremely common. The trailers vary from open trailers for hauling loads to boat trailers and campers. One important requirement, for safety and legal reasons, is that the trailer have appropriate safety lights such as turn signals, brake lights, and running and parking lights. These lights naturally have to be controlled from the vehicle pulling the trailer so the driver can signal those behind the trailer of turns or braking actions before they occur or simply warn vehicles approaching the trailer from behind at night of the presence of the trailer being towed on the road. The trailer safety light circuits usually connect directly into the electrical system of the towing vehicle by standard connectors and wiring methods. The trailer safety light circuits generally work in tandem with the safety light circuits on the towing vehicle. However, the safety lighting circuitry of trailers have a notorious reputation for unreliability and failure. The inability of the vehicle operator to easily check to determine if the circuitry is operating properly only compounds this problem.
Failure of the safety lighting circuits on a trailer can create extremely hazardous situations and the fact that the trailer being towed by the vehicle partially obstructs the `view` of the operator further compounds the problem. In order to verify the proper functioning of all of the safety lighting circuits the vehicle operator needs the assistance of a second party to stand behind the trailer to observe the operation of the safety lighting circuitry while the vehicle operator tests them. In addition to being an awkward method of verifying proper operation of the safety lighting circuitry it does not provide any suitable means to verify the proper functioning of the safety lighting circuitry during actual operation of the vehicle while towing the trailer. Additionally, the vehicle operator can not easily or conveniently test the safety lighting circuitry if he has no one present to assist in the process.
Boat trailers present their own unique problems as a result of their being periodically submerged during the launching and retrieving of the boat which the trailer carries. The safety lighting circuits as a result of the periodic dunking have a tendency to corrode much more easily. Also, the circuit bulbs burn out much more frequently from being immersed in water, during the time they are `on` or activated, due to the vehicle operators inability to easily turn the circuits off.
To further compound the problem, trailers tend to have a low maintenance priority and are often left outside exposed to the elements between use which in many instances can be infrequent